The invention relates to a retaining ring for fastening a target plate in a holding device of a process room, in particular of a vacuum chamber, a target which comprises such a retaining ring and a target plate and a process for its production. Targets are used in various coating processes in which the surface of the target plate is atomized or vaporized by ion bombardment and the particles released are deposited on a workpiece. The target is gradually consumed.
EP-A-0 499 770 discloses a target which is produced as a single piece from target material and has anchoring extensions which project radially outwards and are distributed uniformly over its circumference, separated by spaces and recessed relative to an upper surface of the target and serve for anchoring the target in a holder. The holder has corresponding inward-pointing retaining projections which, after rotation of the target, grip above the anchoring extensions so that said target is fixed in the manner of a bayonet lock, the anchoring extensions additionally being pressed against the retaining projections by a metal foil of a cooling device, which metal foil presses against the underside of the target. This has the disadvantage that the anchoring extensions in each of the relatively rapidly consumed targets has to be produced by a complicated processing procedure, a relatively large part of the often expensive target material being lost in certain circumstances.
It is the object of the invention to provide a target fastening, in which the shape of the target plate consisting of target material need not meet particular demands predetermined by the requirements of its anchoring, and a corresponding target. This object is achieved by the features in the characterizing clause of claim 1 and of claim 6. In addition, it is intended to provide a particularly simple production process for the target. This object is achieved by the features in the characterizing clause of claim 10.
The advantages achieved by the invention are in particular that the target function is decoupled from the anchoring function and therefore at most very simple machining ensuring an adequate connection to the retaining ring performing the anchoring need be carried out on the target material. On the other hand, the retaining ring which carries the anchoring extensions has a complicated shape consists of a resistant material and is reusable. The proposed machining of the target plate is very simple to carry out and results in only small losses of material.